Kerbal Space Shuttle and rocket Economics

[Vegetal]

Oh I see. Cool. I wanted to fly a paraglider someday....

[Alshain]

The problem with Shuttles in KSP is that the real shuttle was more than just a payload lifter, it could be a temporary orbital science lab all by itself. In KSP, they just don't have that function at all, they are pure lifters. So why carry wings, fuselage, and wheels when you can just make a rocket.

Don't get me wrong, I have made some shuttles, for fun, but there is no reason beyond that to use them in KSP.

[Nobody_1707]

Johnny Wishbone-> I think you are a bit too cynical. I doubt it was designed to be a money pit, at least not a money pit per launch.

Sure, the aerospace contracters would like regular business - but they'd get that if there were low refurbishment costs and 50 launches per year, or high refurbishment costs and 2 launches per year.

No, he's exactly right. My dad was an industrial engineer over at the Michoud facility where they built the external tanks. NASA ran the shuttle solely to burn tax dollars. Any real work that the shuttle accomplished was strictly incidental.

The Orion is the same way as evidenced by the fact that they refused to use the pre-existing 40m fabrication tools, despite repeated urging to do so from the people who have to actually build the rockets, until after they'd been in storage for so long that they needed to be completely replaced.

Edited October 11, 2015 by Nobody_1707

[ajburges]

I think that one thing people overlook is that the STS shuttle was overdesigned.

One of its mission profiles was a once around polar flight. Such profiles are trivial for SSTO space planes, but SSTO rockets don't have the cross range for a return to KSC without extra fuel for a normal burn.

Still, the kid size planet makes space access too easy to skip straight to 100% recovery solutions. Any STS shuttle is a few jet engines and some fuel away from being an SSTO solution.

The closest I've come to practical STS shuttles are Duna space planes.

[KerikBalm]

Except I pseudo-SSTO'd my Duna spaceplane:

https://scontent-fra3-1.xx.fbcdn.net/hphotos-xaf1/v/t1.0-9/s720x720/1795678_10103669579445203_6304544089077422022_n.jpg?oh=206fb636b454e108ea1abd63d8271630&oe=56926446

The only problem was that it couldn't launch horizontally, and it didn't have enough thrust (even in 1.02) to launch vertically.

So.. 8xflea SRBs solved that, which landed on the runway because I pitched over as soon as it was off the ground.

Doesn't seem very STS to me... yea it had SRBs... mounted symetrically around the duna spaceplane.

But its engine was only used for orbital insertion (the poodle is more efficient than rapiers).

Actually, the whole thing makes it to orbit after booster seperation, which happens a few seconds after launch.

Basically its RATO assist to get a SSTO spaceplane to launch vertically.

[inigma]

Not very efficient, but certainly STS shuttles are a lot of fun:

And they can really carry a lot of cargo, making these real workhorses (42 tons to 500km orbit is a sweet deal IMHO): (yes that orange tank AND rcs tank are part of a fuel depot that is being lifted full of fuel into orbit, not a drop of it used to do so)

At 451,834 kredits with all but the External Tank recoverable (and you can recover that too if you desire) with a recovery mod, cost per ton is about 2-3k. Not efficient by any stretch but it can pay for itself. If I had gimballed parts that actually worked as well as the engines it has now, and mk3 SRBs with fuel extensions, the cost could very well drop to below 1k per ton to 400km orbit, and the part could would nearly drop to half what it is now. No more SAS stacks to make up for realism, or sacrificing 42 tons to 400 km orbit performance.

These things are so durned beautiful:

Bob Kerman on EVA flying an MMU to attach a solar wing and docking port to Alpha Station

Completed docking to Alpha Station

You can download this latest version of my STS, the STS-7E which has SRBs from KerbalX and everything you see here (except the station): http://kerbalx.com/inigma/STS-7E-Space-Shuttle

Edited October 12, 2015 by inigma

[KerikBalm]

Not very efficient, but certainly STS shuttles are a lot of fun:

Yep, they are.

And they can really carry a lot of cargo, making these real workhorses (42 tons to 500km orbit is a sweet deal IMHO): (yes that orange tank AND rcs tank are part of a fuel depot that is being lifted full of fuel into orbit, not a drop of it used to do so)

I don't ever bother going to a 500km orbit... but 42 tons is not so much.

This is a real "workhorse":

Although that was done in two launches.... the rear section with the KR-2L and 2 nukes went up in this:

https://scontent-mxp1-1.xx.fbcdn.net/hphotos-xlp1/t31.0-8/s720x720/12079947_10103920539299643_7804082981841770667_o.jpg

and the rest went up in this:

https://scontent-mxp1-1.xx.fbcdn.net/hphotos-xpt1/t31.0-8/s720x720/12095269_10103920539404433_7429022844425493780_o.jpg

This was lifted in just 2 launches... last time I calculated... it was like 200-250 per ton (includes the fairing cost)

At 451,834 kredits with all but the External Tank recoverable (and you can recover that too if you desire) with a recovery mod, cost per ton is about 2-3k. Not efficient by any stretch but it can pay for itself.

I don't think so... this doesn't sound appealing because:

#1) I'm looking for all stock solutions, not needing a recovery mod

#2) 2-3k is terrible when a disposable system is getting ~1.2k/ton. Like the Real STS, it does not pay for itself... you lose money on every launch

#3) My all stock solution gets <800/ton... granted, from a sea level launch, it barely makes it to orbit with a 36.2 ton payload (I've got larger margins from launching with it held as high as possible... but I think mainly I just need to get the ascent profile right.

Even my <800 per ton design is terrible compared to a fully SSTO and/or airbreathing design.

If I'm going to spend the time to recover the spaceplane as a glider... I might as well spend a little more time on the ascent, and get a <150 cost per ton, and have propulsion when I deorbit, so its easier to land back at the runway.... with something like this:

Which is <150 per ton, and has a much higher payload capacity (it'll get a 42 ton payload to orbit with fuel to spare)

Seeen here with much less than 42 tons of payload... but placing the payloads at nearly escape velocity to kerbin

Lets not talk about the capabilities of shuttles as being impressive... they aren't. Full SSTOs will beat them. Full disposables will beat them...

Under the right circumstances it seems, they can be more economical than full disposables*... but they'll never be more economical than SSTOs.

* Can anyone make a disposable system for less than 1.2k/ton to LKO?

Seems the way to decrease the cost per ton, is to increase the internal fuel capacity/ the fuel capacity of the ET (although this deviates from the STS aesthetic, because the ET wasn't recovered, and the SRBs were... but due to KSP's mechanics... it seems the inverse is the only stock solution).

That design still gets a decent cost/ton even with no ET recovery.

That was a sea level launch (right above the pad), as opposed to using the launch clamps to hold it over 100 meters above the pad... an earlier launch were I did that has 121 m/s remaining, and a 75km apoapsis.

Ascent profile is really important on that design.

No more SAS stacks to make up for realism, or sacrificing 42 tons to 400 km orbit performance.

My design doesn't have any reaction wheels added (the mk3 had 1 large, the mk4 has none) aside from the cockpit's built in reaction wheels.

Why the obsession with such high orbits? things are scaled down in KSP... if you were playing RSS, I'd see the desire for 400 km orbits... but I rarely go over 110km orbits... and mostly that's because I overshot 100km orbits.

These things are so durned beautiful

It does look nice overall, and certainly more faithful to the real STS look than mine (mine uses 4x SRBs, not 2. It uses 1 liquid engine, not 3). The part clipping and "lego" wing don't look so nice to me though (OCD-ish perhaps?).

I avoid part clipping like the plague... but its a bit unavoidabel that there is some clipping when I rotate the KR-2L... its not so noticeable

You can download this latest version of my STS, the STS-7E which has SRBs from KerbalX

I try to keep everything stock now that 1.0 is out... I use KER, and my own modded electric atmospheric engines (using stock models from .18), and thats it.

[Donziboy2]

My only grip with SSTO's is the extra time needed to land the craft back on Kerbin.....

[KerikBalm]

Which is also present in shuttles....

But the launch is faster than an airbreathing horizontal TO SSTO

[inigma]

What Kerik said. My all-stock STS-7E above is as fast to launch and orbit as a rocket, and as much fun to land as an ssto. The best of both worlds capable of paying for itself thus justifying it as a workhorse for under 42 ton mk3 cargo bay payloads up to 400km orbit. I like to weigh in efficiency with the fun factor as well as the practical factor. Try flying her. You will see what I mean. Accidents are also more fun with the "lego" wings rather than the mk 3 wing parts.

[KerikBalm]

I still don't see how you can say it pays for itself if its costs per ton are over 2k/ton

I can SSTO a normal rocket, and just land it somewhere near KSC, and get lower costs per ton that way.

Of course, as stated multiple times as well, fully disposable systems will beat that cost per ton as well.

[tseitsei]

I still don't see how you can say it pays for itself if its costs per ton are over 2k/ton

I can SSTO a normal rocket, and just land it somewhere near KSC, and get lower costs per ton that way.

Of course, as stated multiple times as well, fully disposable systems will beat that cost per ton as well.

If you can get >2k profit from every ton delivered to orbit it obviously pays for itself...

[inigma]

This thread could use a little STS inspiration. Enjoy.

[KerikBalm]

If you can get >2k profit from every ton delivered to orbit it obviously pays for itself...

Well, by that logic, pretty much any reasonable launcher pays for itself.

If you consider the "opporotunity cost", relative to a straight forward staged launcher... you're losing money each launch... rather losing money you could have had.

[Wahgineer]

Someone should run the numbers on a shuttle C: two main engines instead of three, use fairings instead of a cargo bay (and maybe a mk3 to size 3 adapter as a base), and have it unmanned. Maybe by just recovering the main engine 'pod', we could reduce launch cost.

[tseitsei]

Well, by that logic, pretty much any reasonable launcher pays for itself.

If you consider the "opporotunity cost", relative to a straight forward staged launcher... you're losing money each launch... rather losing money you could have had.

That is true but that is also what "it pays for itself" actually means...

[TimePeriod]

While I could use SSTO's or a shuttle type rocket, I can build a rocket which is half or even 1/4 the prices and just design it to save the most expensive parts. Sure its not a 100% recovery but it is a whole lot simpler, cheaper (pr launch), less part consuming, less part clipping and a whole lot of other things. In my eyes rockets can do everything that the other two types do to a far better degree with acceptable loss.

[KerikBalm]

That is true but that is also what "it pays for itself" actually means...

I disagree... context is everything.

If we take it very very literally... it pays for nothing, it sucks up funds, and give your a service. At no point does it atually directly produce funds.

Just about the only thing to literally pay for itself would be an ISRU setup on the launchpad converting full ore tanks to monoprop or LF.

In the case of the shuttle... or any launcher, whether or not the service it provides is greater than the cost, depends on the value of the service... and that depends on the value of the contract... which varies depending on the contract generated, and the game settings.

So what you then have to amend the statement to is:

"is capable of turning a profit delvering payloads to space for most contracts and settings".... which is a very different thing.

If I'm running a disposable launcher program, and you try to sell me this semi re-usable system, and tell me it pays for itself, I take that to mean that while the initial cost is higher, over time I'll save more than that cost in funds relative to using the disposable launcher...

Which is definitively not the case at 2-3k per ton.

Someone should run the numbers on a shuttle C: two main engines instead of three, use fairings instead of a cargo bay (and maybe a mk3 to size 3 adapter as a base), and have it unmanned. Maybe by just recovering the main engine 'pod', we could reduce launch cost.

Fairings are pretty expensive as they are right now... at least for the size 3 fairings...

For my large SSTOs... 1/3 of the net cost is the fairing... meanwhile a mk3 bay is only 3k.

I've made fairings for large payloads that are over 10k.

The fairings are also quite heavy.

I don't think you save any mass, and I doubt using a fairing instead of a cargo bay will reduce cost per ton.

[Wahgineer]

with the simplified shuttle c, we're cutting out everything: wings, control surfaces, cockpit, landing gear, etc. by replacing these with just a fairing, we could increase payload while decreasing launch cost.

[G'th]

with the simplified shuttle c, we're cutting out everything: wings, control surfaces, cockpit, landing gear, etc. by replacing these with just a fairing, we could increase payload while decreasing launch cost.

The thing about the Shuttle C, while neat, is that it was only a solution to the problem of keeping the Shuttle program going. Because at this point, you may as well just design a regular rocket and design it's stages to be recovered, ala the Inline version of the Shuttle C. By keeping the basic Orbiter-ET-Boosters stack you're really overengineering something that can be done far simpler.

Of course, in KSP that doesn't necessarily matter, but in the same amount of time you'd spend getting the Shuttle C to work in-game, you could have designed an equally funds saving rocket and probably launched it a couple of times. If not an even cheaper one.

[Wahgineer]

true, but for the sake of argument, let's say the launcher has to be shuttle inspired (side boosters, side mounted, etc). If that's the case, then shuttle c is your best bet. But you're also right as well.

[Fiddlestyx]

This thread could use a little STS inspiration. Enjoy.

That was beautiful.